1. Field
Embodiments of the disclosure generally relate to the field of dynamic spectrum access in wireless networks, and in particular, to systems, methods, and devices for primary user sequence detection.
2. Description of the Related Art
Cognitive radio is any radio that may change its transmission behavior based on interaction within the radio environment which it operates. Cognitive radios may perform dynamic spectrum access, which is a method of communication between nodes in a wireless network that takes advantage of inefficient use of already used or licensed radio spectrum. It is well known in the art that total throughput of information transmitted in a radio spectrum can be increased by allowing certain cognitive radio wireless nodes or secondary radio users to transmit when the traditional or primary radio users of the spectrum are idle. Transmission performed in this manner allows multiple wireless radio networks to use the same radio spectrum, thus increasing the exchange of information, while reducing interference to the traditional radio users' use of the spectrum thru “smart” transmission.
Determining when primary radio users are idle and not transmitting in a radio spectrum is called spectrum sensing. One approach is the detection of a pilot signal that is transmitted simultaneously with the traditional user's data. When the pilot signal is detected, the cognitive radio cannot transmit.
Another approach for spectrum sensing is called energy detection. Energy detection is based on the assumption that all radio transmissions, including the primary users' transmissions, have inherent associated energy. The energy can be measured at different radio frequencies across a radio spectrum. After removing the energy associated with out of band noise, an energy detector compares these energy levels to minimum energy level thresholds to determine whether there is enough energy in the primary radio users' spectrum to make the determination that it is the primary radio users' current transmissions that is the cause of the energy. If the energy meets these thresholds or a subset of thresholds, the spectrum is considered occupied by the primary users. However, if the energy thresholds are not met, then the primary users are considered idle and the channel is free. A cognitive radio user can then access the spectrum.